The invention relates to a device for producing sponge iron from iron oxide lumps in a reduction shaft. The device uses a hot dust laden reduction gag which is produced in a gas generator through partial oxidation of solid carbon carriers. The reduction gas is guided via lateral reduction gas inlets at the lower end of the reduction zone into the reduction shaft, in which device the iron oxide lumps are placed in the upper region of the reduction shaft and are delivered radially at the lower end of the shaft as sponge iron by delivery organs.
1. Field of the Invention
In the reduction of iron oxide lumps in a reduction shaft, the sponge iron produced is delivered from the lower portion of the reduction shaft. A possible way described in EP0 085 290 A1 of effecting this delivery consists in the sponge iron being led away by means of radially acting delivery organs, especially screw conveyors, from the side of the reduction shaft furnace. Through the radial arrangement of the screw conveyors, there exists between same lateral intervening spaces (dead areas) which widen towards the inner wall of the reduction shaft. On these intervening space areas are built up unmoved zones of the charge moved downwards through the shaft, so called xe2x80x9cdead menxe2x80x9d. Furthermore it is problematic, making the delivery organs any size in respect of their diameter and length for reasons of solidity, such that normally even in the center of the reduction shaft, between the inner ends of the delivery organs (screw heads) there exists a dead area, on which likewise a xe2x80x9cdead manxe2x80x9d (central xe2x80x9cdead manxe2x80x9d) builds up. The height of these xe2x80x9cdead menxe2x80x9d depends on the size of the respective intervening space area and the fill angle of the charge poured. In particular, with high dust cover as a result of the dust content of the reduction gas, this fill angle is very steep and the inner friction is very high. The xe2x80x9cdead menxe2x80x9d formed over the intervening space areas of the screw conveyors and the central xe2x80x9cdead manxe2x80x9d can support one another. The xe2x80x9cdead menxe2x80x9d have a potentially harmful influence on the uniformity of the gasification of the charge and on the charge movement in the shaft and thus on the uniformity of the reduction of the iron oxides.
2. Description of the Related Art.
EP 0 166 679 A1 describes an arrangement of a melting gasifier and a direct reduction shaft furnace with a fill of iron oxide lumps in which the shaft furnace has a base to support the packed column, delivery openings in the base to deliver the sponge iron particles and at least one inlet for the reduction gas delivered from the gasifier into the lower section of the packed column. Since the reduction gas is very dust laden, there is a danger of the free spaces in the packed column being blocked up with the consequence of a corresponding increase in the resistance to the passage of the reduction gas. In order to make it possible for even a gas laden with a larger proportion of dust to be supplied from the gasifier directly into the reduction shaft furnace, without adding to the spaces in the packed column and consequently leading to uneven gas distribution in the shaft furnace and therefor to operation breakdowns, radially disposed screw conveyors are provided to move, mutually and constantly, the particles of the fill backwards and forwards in the region through which reduction gas flows, adjacent to the inlet for the reduction gas, and furthermore at least one delivery opening is arranged respectively at the opposite ends of the screw conveyors in the base. The drive of the screw conveyors can be realized in that either the individual screws are rotated in succession in both directions, or a combination of screws conveying constantly outwards and constantly inwards is provided.
In this arrangement, both the delivery opening are shielded vis-xc3xa1-vis the packed column; the outer one by an annular apron and the inner one by a cone. The cone ends shortly above the screw conveyors or it contains entry apertures in which the inner ends of the radially disposed screws engage. By this means it is ensured that the sponge iron does not reach the delivery openings directly, i.e. without additional conveying organs, but can only be transported to the openings by means of the screw conveyors. This is necessary in order to produce the backwards and forwards motion of the sponge iron.
Since the poured charge is also supported on the cone shielding the central delivery opening, the appearance of xe2x80x9cdead menxe2x80x9d is also probable here.
Proceeding from EP 0 166 769 A1, it is therefore the object of the present invention to create a device for producing sponge iron from iron oxide lumps in a reduction shaft using a hot dust laden reduction gas, which is produced in a gas generator by partial oxidation of solid carbon carriers and is led via lateral reduction gas inlets into the reduction shaft at the lower end of the reduction zone, in which device the iron oxide lumps are placed in the upper region of the reduction shaft and are delivered radially at the lower end of the shaft by delivery organs, and in which device additional delivery opening for thesponge iron is provided in the base of the reduction shaft in the central region of the reduction shaft below the area formed between the inner ends of the delivery organs, in which device the building up of a xe2x80x9cdead manxe2x80x9d is avoided at least over the area situated in the center between the radial delivery organs.
This object is achieved according to the invention by providing an additional delivery opening for the sponge iron in the base of the reduction shaft in the central region of the reduction shaft below the area formed between the inner ends of the delivery organs, wherein the delivery organs are provided to convey the sponge iron only radially outwards. Additional advantageous developments are described herein.
Because the delivery organs are provided to convey the sponge iron only radially outwards, no backwards and forwards motion of the sponge iron takes place on the base of the reduction shaft and the central delivery opening does not have to be shielded, such that xe2x80x9cno dead menxe2x80x9d can be formed any more in the center nor substantially also laterally between the delivery organs, since the central area itself serves as a delivery opening and also the charge material situated above the lateral surfaces can no longer be supported on the central xe2x80x9cdead manxe2x80x9d, but rather is guided as it sinks in the reduction shaft to a considerable extent to the additional delivery opening.
Advantageously, a guiding device is provided between each two delivery organs and extends upwards beyond same, in such a way that the sponge iron sinking downwards is guided laterally to the delivery organs and radially to the additional delivery opening. By this means increased guiding of the charge material to the delivery organs and the additional delivery opening is achieved.
The guiding devices preferably have an upper edge running obliquely upwards from the edge of the additional delivery opening to the inner wall of the reduction shaft, and widen downwards and radially outwards to the width of the lateral space between the delivery organs. By this means it is ensured that the whole charge material sinks uniformly downwards until it is delivered.
Through the division of the discharge into an external and central region, the sinking speed in the region of the shaft outer diameter and in the region above the central delivery can be controlled independently of one another. Thusxe2x80x94in conjunction with the individually adjustable delivery speeds of the delivery organsxe2x80x94purposeful control of the shaft action is possible over the whole shaft cross-section.
Advantageously there is located below the additional delivery opening a vertical shaft with a diameter which is constant and corresponds to the diameter of the delivery opening, the shaft being closed at the lower end, and at least one further delivery organ for the sponge iron, acting radially, being disposed above the base of the shaft.